在分隔符上拆分字符串，在拆分之前保留分隔符

Question

问题R split on delimiter (split) keep the delimiter (split) 的明显扩展是： 如何拆分字符串，将分隔符保留在每个部分的开头？

x <- "What is this?  It's an onion.  What! That's| Well Crazy."

解决方案

unlist(strsplit(x, "(?<=[?.!|])", perl=TRUE))

给予：

"What is this?"    "  It's an onion." "  What!" " That's|" " Well Crazy."

而我正在寻找：

"What is this"    "? It's an onion" ".  What" "! That's" "| Well Crazy."

将积极的lookbehind改为积极的lookahead并不能解决问题。

Answer 1

我设法解决了这个问题，方法是使用积极的前瞻，然后是一个单词边界标记：

x <- "What is this?  It's an onion.  What! That's| Well Crazy."
strsplit(x, "(?=[?.!|].)\\b", perl=TRUE)

[1] "What is this"     "?  It's an onion" ".  What"          "! That's"        
[5] "| Well Crazy."

Demo